Study On The Difference Of Rice Tillering Nitrogen Response On Different Region Soils

There are great differences in the amount of nitrogen applied on the soil in different regions,and there are also some differences in the nitrogen response of tillers,but the reasons are not completely clear.A pot experiment was conducted in the potting field of Northeast Agricultural University in Harbin,Heilongjiang Province.three levels of N application were set up in black paddy soil（collected in Wuchang City,Heilongjiang Province,127°15’E,44°92’N）,red paddy soil（collected in Changsha City,Hunan Province,112°98’E,28°19’N）,and gleyed paddy soil（collected in Nanjing City,Jiangsu Province,118°22’E,31°14’N）:N0:no N fertilization;N1:0.87g.N.pot^-1(equivalent to 150 kg.N.hm^-2);N2:1.74 g.N.pot^-1(equivalent to 300 kg.N.hm^-2).Soil inorganic N,soil microbial diversity,soil mineralized N,rice hormone content（CTK,IAA,ABA）,plant nutrients（N,P,K）,tiller number,tiller angle,plant dry weight,SPAD,rice yield,and rice N efficiency were measured.The effects of soil and N amount on rice tiller number,yield,and N efficiency were investigated to reveal the reasons for the differences in N response of rice tillers on different soils.The main experimental results were as follows:（1）Both N amount and soil had significant effects on rice tillering.Under the condition of no N application,the number of tillers increased by 10.21%-37.18%（P<0.05）in red paddy soil and45.20%-77.11%（P<0.05）in black paddy soil compared with gleyed paddy soil.The number of rice tillers in July increased by 17.84%-30.69%（P<0.05）in black paddy soil at different N levels compared with that in red paddy soil.The number of rice tillers at maturity was 13.04%（P<0.05）and 16.35%（P<0.05）higher in 2021 for the black paddy soil compared to the gleyed paddy soil at N1 and N2 levels,respectively.Overall,there was a trend of earlier peak tillering in the no N application treatment relative to the N application treatment.（2）The number of rice tillers was significantly and positively correlated with soil inorganic N content and leaf N content.When no N was applied,inorganic N was higher in black soil-type rice soils,but leaf N content was lower than that in red paddy soil.After N application,the inorganic N content of red paddy soil increased rapidly and was significantly higher than that of black paddy soil and gleyed paddy soil,at the N2 level.The reason for the rapid increase of tillering in red paddy soil was related to its higher mineralization capacity and high leaf N content throughout the period.On all three soils,red paddy soil had higher SPAD,and leaf nitrogen content was higher in red paddy soil than in black soil,and in black soil than in gleyed paddy soil.2020 yield was higher in red paddy soil and 2021 yield was higher in black paddy soil.Although the number of tillers was significantly lower in the gleyed paddy soil,than the other two soils,its yield in 2020 was not significantly different from that of the black paddy soil,and the difference with the red paddy soil in 2021 was not significant.（3）Proteobacteria plays an important role in the nitrogen cycle,and the soil microbial diversity index was negatively correlated with rice tillering.For this index of microbial species in soil,the content of Proteobacteria phylum and others showed that:red paddy soil>gleyed paddy soil>black paddy soil.For Amoeba phylum,the amount of N suitable for growth on the three soils differed,with the highest contents on N2,N0,and N1 on black soil type,red soil type,and gleyed paddy soil,respectively,which may be the reason for the higher tillering on red paddy soil without N application and the increase of tillering on black paddy soil with the increase of N.On black paddy soil,ACE and Chaos showed significant negative correlations with rice tiller number;on gleyed paddy soil,Shannon showed significant negative correlations with rice tiller number,and the correlations were weaker under other conditions.（4）Higher values of CTK/IAA at different N application levels were more favorable for rice tillering.However,most of the CTK/IAA did not differ significantly between soils,and only in2020 the red paddy soil was significantly higher than the other two soils.With the increase of N,the CTK/IAA values of rice tiller nodes increased,thus promoting the number of rice stems and tillers.The relationship between CTK content of rice tiller nodes and rice tiller number was not consistent across soil types and there were interannual differences.IAA and ABA content were significantly and negatively correlated with rice tiller number,and higher ABA acted as a suppressor of rice tillering on gleyed paddy soil.